The high dynamic characteristics of Unmanned Aerial Vehicle(UAV) result in null mismatch of Adaptive Sidelobe Cancellation (ASLC), which directly reduces the interference suppression effectiveness of the ASLC system. To address this issue, a Gaussian-distributed tapering matrix null broadening algorithm is integrated into the ASLC technology, aiming to solve the mismatch problem between the interference signal DOA and the null steer in high dynamic environments. By assuming that the DOA of the interference signal follows the Gaussian distribution, the tapered autocorrelation matrix and cross-correlation matrix are derived analytically based on the Minimum Mean Square Error (MMSE) criterion. Simulation results demonstrate that the proposed algorithm achieves a 20% increase in null broadening width at -50dB null depth compared to the uniform distribution null broadening algorithm.